A couple of points. First YOU are the PIC, not the inspector. If you have a safety concern,discuss it with him before you do it. In Part 23 aircraft like the Baron, every FSDO I have dealt with, pulls the engine back slowly, with the throttle around 500 AGL. In the FAA's own training material for their inspectors, Oklahoma City actively Discourages the pulling of the mixture. For good reason.
Next Be comfortable with the Operations Manual including the Ops Specs. Know how to do the flight log, how to write up a mechanical, how it is suppose to be clared, how to use the MEL. Know who the required managemet personnel are. As for Op Specs. Know the items you use every day. Weather, alternate minimums and no alternate, fuel requirements, approved approaches, etc. You will be expected to know that. Stuff you do not use every day, like lower than standard takeoff minimums, eligible on demand flight crew and so on, you will be expected to know where to find them. Section A is general, Section B is enroute, Section C is approach, Section D is Maintenance and Section E is weight and Balance. Since you are in a Baron, I am assuming this ride is single pilot. So I wouldn't worry too much about Section E as that applies to aircraft with 10 or more passenger seats and have an approved weight and balance program. You also are not able to use lower than standard take off minimums.
If you do not know the answer, them the inspector you do not know. Then tell him where you would look for the answer. They like that. They do not expect you to know everything. Give them just the information they ask for and move on. No BS, etc.
Good luck.